Introduction to Particle (for non physics students) 2. PARTICLES (from atoms to quarks and leptons) Structure of Matter

Two ways that structure is revealed:

True from atoms to particles….. Spectra

Qualitatively similar Spectra

Quantitatively different Scattering

Nuclear atom

Proton/neutron

Quarks

Qualitatively similar Rutherford: Nuclear Atom

Alpha particles from natural radioactivity

Gold leaf

Small scintillation screen Rutherford used energy conservation… …and long division ..and how Rutherford used them Quarks in the proton

Qualitatively: Same idea

Quantitatively: Different scale SLAC 3km electron accelerator

The BEAM Quarks in the proton

Electron beam = 3 km

Proton target (hydrogen)

Big electronic detector TARGET DETECTOR

BEAM me Proton made of 3 quarks, gripped by To make proton and neutron requires two “flavours” of Quarks

Up and down Quarks and neutron ddu H atom (not to scale!) a miracle of neutrality electron balances uud hint of unification

beta decay at quark level

Stars cook the elements

Sun is dominantly this first step

Heavy elements cooked in stars and ejected into cosmos in supernova explosion

Many protons; electrical disruption Stabilised by STRONG force

How do we know the is produced?

It hits a nucleus upstream and turns into charged lepton which is detected.

Three charged leptons electron muon And three neutral: e-neutrino mu-neutrino tau-neutrino

Neutrinos and their e-neutrino electron charged partner mu-neutrino muon are always linked tau-neutrino tau if are massless BUT if neutrinos have mass, they can oscillate back and forth

Neutrino Oscillations

• Nu beams from lab (CERN,,KEK) • Measure intensity nearby • Measure 100s km away

• Evidence that nu are disappearing • Direct evidence for oscillation not yet

• Major research programme to understand neutrinos- masses, mixing, key to pattern of the three generations?

• Muon-neutrino Nature’s Three Party System Spectra

So are quarks (and leptons) also composites? MATTER quarks electron neutrino leptons

ANTIMATTER antiquarks ANTIMATTER positron antineutrino antileptons MATTER qqq proton

ANTIMATTER ANTIMATTER qqq antiproton leptons MATTER qqq proton BARYONS

q MESONS q

ANTIMATTER qqq antiproton ANTIBARYONS A Very Short Introduction Coming out in December NEW More in Vsi

And particle odyssey The Particle Odyssey TheA Journey Particle to the Heart Odyssey of matter

Frank Close, Michael Marten,